Chris Sutton kirjutas T, 04.03.2003 kell 17:03: > Hello, > > I need some insight on the best way to use a RAM drive in a Postgresql > installation. Here is our situation and current setup: > > Postgresql 7.2.1 > Dual PIII 800 > RAID 5 SCSI disks > Platypus 8GB PCI QikDrive (the RAM drive). http://www.platypus.net > > The Platypus RAM drive is a PCI card with 8GB of ram onboard with an > external power supply so if the main power to the server goes off, the RAM > is still powered, so it's persistent between reboots. > > Currently the disk size of our database is 3.2GB, so we put the whole > pgsql directory on the RAM drive. Current preformance is very > snappy with the bottleneck being the CPUs. > > The concern of course is if something happends to the RAM drive we are > S.O.L. and have to go to the last backup (pg_dump happens each night). > > The other concern is if the disk size of the database grows past or near > 8gb, we would either have to get a bigger RAM drive or somehow split > things betten SCSI and RAM drive. > > I don't quite grasp the full inner workings of Postgresql, but > for those of you who obviously do, is there a better way of setting things > up where you could still use the RAM drive for portions of the pgsql > directory structure while putting the rest on disk where it's safer? > > Should we just put pgsql/data/pg_xlog on the RAM drive? > > Also, in the very near future we will be upgrading to another server, > pg7.3.2 with dual P4 2.4 xenon's. The RAM drive will go into this new > server. > > Any suggestions?
The most obvious suggestion is to put the WAL files on RAM disk - these are the things that would most directly affect _write_ performance as these are the only ones the *must* hit the disk befor the transaction can be committed. If you are after read performance, then you just ;) have to determine which are the most frequently used files that are not reasonably cached . --------------- Hannu ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster